The present invention relates to an apparatus and method for sealing a sheet of covering material onto a container. More particularly, the present invention relates to an apparatus and method for ultrasonically sealing a sheet of covering material to a flange of a continuously moving container.
Containers for holding various products are often formed from paperboard, plastic, or a similar materials in a die press or thermoform machine. The containers are typically formed from flat paperboard blanks which have been scored in predetermined areas to facilitate formation of the containers. The scored sections reduce the likelihood that the blanks will tear as the containers are formed. Others are molded from sheet or resin. The containers are used to hold various products such as food.
Various types of automated systems are known for automatically filling containers moving along a predetermined path with a product such as food or the like. Containers are typically transported in metal container carriers along an assembly line path in a predetermined direction on a conveyor. A roller chain or other suitable drive means is used to move the container carriers along the assembly line path.
Individual containers which contain one or more servings of food and are sold either refrigerated or frozen are becoming increasingly popular. Such containers are typically processed on an assembly line, with the filling of the containers usually being accomplished with overhead buckets, funnels, spouts, or the dispensers that disburse a metered amount of the product into each individual container. See, for example, U.S. Pat. Nos. 4,699,297; 4,498,358; 4,678,015; and 4,823,988.
In some instances, a continuous sheet of material is used to cover and seal the containers. After the product is placed in the container, the sheet of material is sealed to the top of the containers and then cut. In other instances, individual container covers may be placed on the containers before sealing. Packaging devices often use heat sealing assemblies to heat seal the sheet of material or the covers to a flange of the containers. See, for example, U.S. Pat. Nos. 4,490,961; 4,807,424 and 4,991,375.
It is desirable to provide a continuous tight seal between the containers and the covering material. If areas between the container and covering material are not tightly sealed, oxygen or other contaminants can pass into the container and cause the food to spoil. Therefore, it is desirable to reduce the contact of oxygen or other contaminants with the contents of the container in order to increase the shelf life for the food item stored in the container.
Ultrasonic pulses are used in the illustrated embodiment of the present invention to seal the covering material to the flange of the containers. The ultrasonic sealing method of the present invention advantageously increases the speed of sealing the covering material to the containers as compared to conventional heat sealing assemblies. In addition, as the covering material for sealing containers becomes more sophisticated, known heat sealing techniques become less effective. Specifically, the covering material for sealing the containers can be a fiberboard lid which is printed to look visually attractive. These fiberboard lids are typically somewhat insulated. Therefore, the use of heat to seal the fiberboard lid is limited by the insulation of the lid. In addition, heat can damage the inks used to print information on the lids. The ultrasonic sealing method of the present invention facilitates sealing the fiberboard lids or other somewhat insulated covering materials to the containers. The ultrasonic sealing method of the present invention also permits the covering material to be sealed to the container flange through contaminants or excess food which may be located on the flange or the covering material.
Various types of ultrasonic sealing assemblies are known for welding two pieces of material together. It is known to provide a rotating roller which presses at least two sheets of material against a top surface of an ultrasonic vibrating head to weld the two sheets of material together. See, for example, U.S. Pat. Nos. 4,333,791 and 3,088,343. It is also known to provide a rotating welding disk or wheel coupled to an ultrasonic frequency transducer to transmit ultrasonic vibrations to the welding disk. In these known devices, the ultrasonic welding wheel presses two pieces of material against a solid support surface to ultrasonically weld pieces of material together. See, for example, U.S. Pat. Nos. 3,217,957; 3,360,850; and 5,082,160.
According to one aspect of the present invention, an apparatus for sealing a covering material to an outer flange of a container includes a sealing assembly having a horn and means for applying pressure to the outer flange and to the covering material against the horn. The apparatus also includes means for moving the container relative to the sealing assembly so that the outer flange of the container and the portion of the covering material positioned over the outer flange pass below the horn. The apparatus further includes means for adjusting the angle of the horn relative to the covering material and outer flange of the container. In addition, the apparatus includes means for vibrating the horn at a predetermined frequency to cause friction between the outer flange of the container and the portion of the covering material positioned over the outer flange to seal the outer flange to the covering material as the outer flange of the container and the portion of the covering material positioned over the outer flange pass below the horn.
In the illustrated embodiment of the present invention, the apparatus also includes means for reorienting the container relative to the sealing assembly. The apparatus further includes means for moving the reoriented container relative to the sealing assembly so that a second portion of the outer flange of the container and a portion of the covering material positioned over the second portion of the outer flange pass between the horn and the pressure applying means to seal the second portion of the outer flange to the covering material.
Also in the illustrated embodiment, the pressure applying means includes a wheel assembly having a rotating wheel which engages the outer flange of the container as the horn engages the covering material. A cylinder is coupled to the wheel assembly for moving the wheel assembly toward the horn so that the wheel applies a predetermined amount of pressure to the outer flange and to the covering material against the horn as the outer flange and the portion of the covering material positioned over the outer flange pass between the horn and the wheel. The wheel includes an edge surface for contacting a bottom surface of the outer flange of the container. The wheel is also formed to include a plurality of notched sections to prevent the edge surface from engaging the horn when the outer flange of the container and the portion of the covering material positioned over the outer flange are not located between the horn and the wheel.
In another embodiment of the present invention, the pressure applying means includes a container carrier for aligning the covering material relative to the container so that a portion of the covering material is positioned over the outer flange of the container. The container carrier has a top surface which engages the outer flange of the container as the horn engages the covering material.
The sealing assembly still further includes a guide bar having a ramp surface for forcing the covering material downwardly against the outer flange of the container. The guide bar is formed to include an aperture therein to permit the horn of the sealing assembly to extend through the guide bar and contact the covering material.
According to another aspect of the present invention, an apparatus is provided for sealing a covering material to an outer flange of a container including a first pair of opposite sides and a second pair of opposite sides. The apparatus includes a first pair of sealing assemblies for sealing the first pair of opposite sides of the outer flange of the container to adjacent portions of the covering material along a first pair of seam lines, and a first conveyor for transporting the container in a first direction through the first pair of sealing assemblies. The apparatus also includes a second pair of sealing assemblies for sealing the second pair of opposite sides of the outer flange of the container to adjacent portions of the covering material along a second pair of seam lines, and a second conveyor for transporting the container in a second direction through the second pair of sealing assemblies.
The first pair of seam lines overlaps the second pair of seam lines at corner portions of the container to form a tight seal between the covering material and the outer flange of the container. In the illustrated embodiment, the first conveyor continuously moves the container along a first predetermined path relative to the first pair of sealing assemblies and the second conveyor continuously moves the container along a second predetermined path relative to the second pair of sealing assemblies. The first conveyor is aligned at a predetermined angle relative to the second conveyor, and an end portion of the first conveyor is located adjacent the second conveyor so that containers move off the end portion of the first conveyor and onto the second conveyor.
According to yet another aspect of the present invention, a method for sealing a covering material to an outer flange of a container includes the steps of placing a covering material over the container flange, and providing a sealing assembly including a horn and means for applying pressure to the outer flange and to the covering material against the horn. The method also includes the steps of moving the container relative to the sealing assembly so that the outer flange of the container and a portion of the covering material positioned over the outer flange passes between the horn and the pressure applying means, and vibrating the horn at a predetermined frequency to cause friction between the outer flange of the container and the covering material as the outer flange of the container and the portion of the covering material positioned over the outer flange moves between the horn and the pressure applying means to seal the outer flange to the covering material.
This sealing method further includes the steps of reorienting the container relative to the sealing assembly, and moving the reoriented container carrier relative to the sealing assembly so that a second portion of the outer flange of the container and a portion of the covering material positioned over the second portion of the outer flange pass between the horn and the pressure applying means to seal the second portion of the outer flange to the covering material. The method still further includes the step of controlling the amount of pressure applied by the pressure applying means to the outer flange and to the covering material against the horn.
According to still another aspect of the present invention, a method for sealing a covering material to an outer flange of a container includes the steps of placing a covering material over the container flange, and providing first and second spaced apart sealing assemblies, each sealing assembly including a horn and means for applying pressure to the outer flange and to the covering material against the horn. The method also includes the steps of moving the container relative to the sealing assemblies so that outer flanges of the container adjacent a first pair of opposite sides of the container and the covering material pass between the horns and the pressure applying means of the first and second sealing assemblies, and vibrating the horns of the first and second sealing assemblies at a predetermined frequency to cause friction between the outer flanges of the container and the covering material as the outer flanges of the container and the portions of the covering material positioned over the outer flanges move between the horns and the pressure applying means of the first and second sealing assemblies, respectively, to seal the outer flanges of the container adjacent a first pair of opposite sides of the container to the covering material.
This sealing method further includes the steps of providing third and fourth spaced apart sealing assemblies, the third and fourth sealing assemblies each including a horn and means for applying pressure to the outer flange and to the covering material against the horn. The method still further includes the steps of orienting the container relative to the third and fourth sealing assemblies, and moving the oriented container relative to the third and fourth sealing assemblies so that outer flanges of the container adjacent a second pair of opposite sides of the container and the covering material pass between the horns and the pressure applying means of the third and fourth sealing assemblies, respectively. In addition, the method includes the step of vibrating the horns of the third and fourth sealing assemblies at a predetermined frequency to cause friction between the outer flanges of the container and the covering material as the outer flanges of the container and the portions of the covering material positioned over the outer flanges move between the horns and the pressure applying means of the third and fourth sealing assemblies to seal the unsealed portions of the outer flanges of the container adjacent a second pair of opposite sides of the container to the covering material.
In both the apparatus and method of the present invention, the horns used to seal the covering material to the flange of the container are aligned at a predetermined angle relative to the covering material. Preferably, the predetermined angle is adjustable relative to the covering material. By adjusting the angle of the horns relative to the covering material, the apparatus and method of the present invention permit the sealing assembly to operate at higher pressures and higher speeds. In addition to applying pressure to the covering material, the angled horns also help to propel the covering material in a direction of movement of the container. This reduces the likelihood that the covering material will bunch up at the horn.
Additional objects, features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.